The aim of this research is to develop an understanding of why people become vegetarian and why the diet is currently enjoying a steady increase in popularity in contemporary Britain, through addressing the 'hidden agenda' of vegetarianism. Vegetarianism offers an example of food choice which highlights the non-nutritional aspects of food and eating, and represents far more than a pragmatic aversion to eating meat. The research incorporates both qualitative and quantitative studies. Two data sets were collected from 137 vegetarians in Greater London; qualitative information about the values and attitudes of vegetarians regarding diet, health and related issues, and quantitative information regarding the dietary intake of different categories of vegetarian. The findings of both studies are presented, but the thesis focuses on the qualitative data which was analysed using a symbolic approach to the study of food and eating as developed within anthropology. It was found that the decision to become vegetarian, and attitudes regarding food and health, formed a complex package of ideas which ranged from concrete issues, such as concern about the quality of the food supply, to ethical and abstract concerns, such as the character of the relationships between human society, nature and the animal world. There were differences between types of vegetarian in both diet and attitudes; as the diet became more extreme (excluding more animal foods) so attitudes became progressively more heterodox. It is concluded that vegetarianism does not deserve the label of 'fad' or 'cult' diet, but that it articulates a complex and potentially subversive ideology and demonstrates the need to incorporate social and cultural factors into analyses of food choice.